Answer:
On the left side, she used commutative property
On the right side, she used distributive property
Step-by-step explanation:
Let x be the rate of the slower bicyclist and
x + 4 be the rate of the faster bicyclist
Since the bicyclists are headed towards opposite directions, the sum of the distances they covered traveling for one hour and 15 minutes should be equal to 40 km based on the given conditions above. This may be expressed as,
(x)(1.25) + (x + 4)(1.25) = 40
Calculating gives x = 14
Thus, the rate of the bicyclists are 14 km/h and 18 km/h.
I'm sorry I'm too lazy to read all of that. However, I did get the main point. The river was going at 3 mph. Since he wanted to travel 10 miles upstream and downstream, you would have to subtract 20 by 3. This would mean he was going at a speed of 17 mph.